With just one holiday weekend between now and Tuesday's Republican presidential caucuses in Iowa, there's another poll signalling that it could be a close battle at the top between former Massachusetts Gov. Mitt Romney and Rep. Ron Paul (R-Texas). And also once again, former Sen. Rick Santorum of Pennsylvania is on the rise and showing up at No. 3.

The NBC News-Marist Poll has Romney drawing support from 23 percent of the "likely caucus-goers" surveyed. Paul was at 21 percent. Santorum was at 15 percent.

Over at The New York Times' Five Thirty Eight blog, analyst Nate Silver says Santorum "can make the most credible claim of any candidate about having momentum in the state." And he speculates about the chances that the GOP race will come down to a two-way battle between Romney and Santorum.